1. Field of the Invention
This invention relates to a method by which smoke is produced by a smoke generating machine and used to detect leaks (e.g. holes) in a fluid system. The method disclosed herein has particular application for detecting the presence and location of small leaks by leaving a fluorescent trace at the site of the leak.
2. Background Art
It is known to generate smoke within a sealed chamber of a smoke generating machine so that the smoke can be delivered to a fluid system under test in order to detect the presence and location of leaks by visually inspecting the system for any smoke escaping therefrom. By way of example, our prior U.S. Pat. No. 5,922,944 issued Feb. 9, 1999 described such a smoke generating machine that has particular application for producing smoke to identify the presence and location of relatively large leaks in the fluid system.
However, it has been found that in situations where the leaks to be identified are of very small size, a correspondingly small volume of smoke may escape through the hole. In other cases, the velocity of the smoke which escapes the leak may be so high as to make the smoke substantially invisible. As a consequence of the foregoing, small leaks in a fluid system under test may escape detection and repair with the obvious results that the system will operate in an inefficient manner.
In the past, attempts have been made to use a fluorescent dye to accurately locate small leaks in certain air transporting systems. For example, a fluorescent dye has been used successfully to locate leaks in various refrigeration and air conditioning systems. Reference may be made to U.S. Pat. No. 5,918,269 issued Jun. 29, 1999 for an example of a particular dye which is suitable to leave a fluorescent trace at the site of a leak. In this case, the system coolant (i.e. freon) acts a carrier for the dye. Without a suitable carrying agent, it would not be possible to cause the dye to traverse the system so as to mark the location of all of the leaks.
However, there are other air transporting systems, particularly those found in motor vehicles, which do not use a carrier agent. That is to say, the air which traverses these systems is not, and of itself, capable of functioning as a carrier to transport the fluorescent dye past the sites of the leaks. While attempt has been made to vaporize the dye into a mist to improve flow conditions, these attempts have proven to be largely unsuccessful.
Accordingly, what is needed is a reliable, easy to use means of locating relatively small leaks in an air transporting system, such as those found in a motor vehicle, by causing a fluorescent dye to be carried through the system so as to leave a visible trace at the site of the leak, which trace may be quickly detected under ultraviolet light.
In a method to accomplish the foregoing, it has been found that smoke functions as a suitable agent to carry a fluorescent dye through a fluid (e.g. air) system so as to leave a fluorescent trace at the site of each leak. By way of example, a smoke generating machine may be coupled to the evaporative or air brake system of a motor vehicle to locate small holes therein. The smoke generating machine includes a sealed chamber which contains a supply of non-toxic petroleum based oil. In accordance with the present invention, a commercially available fluorescent dye is mixed into the oil within the sealed chamber. A resistive heating grid extends laterally across the chamber of the smoke generating machine above the mixture of oil and dye. A supply of air or, in the alternative, a non-flammable gas (e.g. nitrogen) is delivered to the chamber by way of an air inlet tube. Some of the mixture of oil and dye is drawn into the air inlet tube and blown outwardly therefrom towards the heating grid. As the mixture strikes the heating grid, it is instantaneously vaporized into smoke. The rising smoke within the chamber is delivered via an air outlet tube to the system to be tested. The smoke acts as a reliable carrier of the fluorescent dye through the system and past the site of any leak.
As the smoke from the smoke generating machine travels through the fluid system under test, some of the smoke will escape through a leak (e.g. a hole). The smoke will condense as it escapes through the hole, and the fluorescent dye that is carried by the smoke will leave a detectable trace surrounding the hole. The hole may now be quickly, easily and accurately detected by simply running a source of ultraviolet light along the system. In the event that the system contains a hole, the ultraviolet light will illuminate the fluorescent trace left by the dye which escapes with the smoke through the hole. The trace will now be visible, whereby the presence of the hole can be located and repaired.
FIG. 1 shows a smoke generating machine within which a mixture of oil and fluorescent dye is vaporized to produce a supply of smoke to be delivered to a fluid (e.g. air) system under test for leaks; and
FIG. 2 is an example of a fluid system under test having a leak that is surrounded by a fluorescent trace that is left by the fluorescent dye which is carried by the smoke as it escapes through the leak.